There are also some side effects to using eucalyptus oil. Depending on the individual, a skin rash could occur. If a person does not take the recommended dose, they could experience nausea, diarrhea, abdominal pain and vomiting. Sever overdosing on a product containing eucalyptus oil can cause seizures, internal bleeding, heart problems, difficulty breathing, muscle weakness, slurred speech, drowsiness and low blood pressure, or put the individual in a coma. Pregnant woman, people with heart, asthma, hypertension or diabetes should not take products containing eucalyptus oil. The main concern about taking eucalyptus oil or products containing eucalyptus oil is the dosage. If taking or used correctly, no problems should occur.